二氧化鈦光電陽極之製備及以實驗設計法決定雙陽極系統處理水中偶氮染料之最佳操作參數

Abstract

常見用於處理染料廢水之高級氧化處理技術主要包含：傳統芬頓反應及光催化反應，然而這類型處理方法於反應過程中需添加大量化學試劑，導致在操作成本上偏高且會於反應過程中產生二次污染等問題；因此近年來已有許多研究以電輔助之高級氧化處理技術以解決上述所產生問題且經驗證後可以更有效地脫色，其中又以光電催化反應及電芬頓反應有極佳之表現，故本研究藉由結合兩種不同電輔助之形式以協助提升其效率亦解決二次污染等優勢，開發出一套由光電催化結合電芬頓之新穎雙陽極系統。 因此，本研究大致分為兩個部分，第一部分主要探討三種不同光電陽極之製備(電泳沉積法、直接鍛燒氧化法及陽極氧化法)並利用表面特性及電化學分析選出其最佳化之電極製備程序，而第二部分為利用實驗設計(包含部分因素設計法、最陡上升路徑法及中央合成設計)探討八種不同操作參數(如：溶液中pH、施加電壓、陰極面積、曝氣流量、光照強度、電解質比例、離子強度及初始濃度)對於雙陽極系統處理含偶氮染料(Orange G)脫色效能之影響程度。 結果顯示，第一部分最佳化電極製備程序，以陽極氧化法所製備出來之光電陽極具有較佳光電流效能，其主要原因為結構屬於1-D結構，故其有較短之傳遞路徑且可有效避免電子電洞對之再結合。第二部分主要藉由實驗設計以有效提升染料Orange G脫色降解效能，於部分因素設計中發現溶液中pH、陰極面積、電解質比例及初始濃度對於染料脫色降解影響較為顯著。而後利用最陡上升路徑法及中央合成設計進一步發現，影響染料脫色降解系統中最顯著因素為溶液中之pH，並於相同條件下當系統藉由控制最佳條件pH 2時，可獲得較佳染料降解脫色效果。

The conventional advanced oxidation processes (AOP) for dye wastewater treatment principally comprise traditional Fenton reaction and photocatalytic reaction. However, the use of these methods are disadvantageous because their operation are relatively expensive and possessing problems such as the need of continuous addition of the chemical reagent and further treatment for the iron sludge produced during the process. Recent studies have made some efforts to solve the above problems as well as to achieve a more effective decolorization as well as degradation in the aqueous solution especially by applying photo-electrochemical methods. Therefore, in this study we developed a novel dual anode system, a combination of photoelectro-catalysis (PEC) and electro-fenton reaction (EF). It combined two different forms of electric auxiliary to assist in improving their efficiency and also to solve the secondary pollution problem. The first of two parts of this study focused on the selection of an optimum preparation procedure from three different photoanode preparation methods applied (electrophoretic deposition, direct calcination and anodization). Furthermore, analysis of surface and electrochemical properties were performed to determine the characteristics of photoanode produced from the preparation procedure selected. The second part of this study was the optimization of eight operating parameters (pH, applied voltage, cathode area, aerated flow, light intensity, ratio of the electrolytes, ionic strength and initial concentration) in the dual anode system for azo dye treatment in the aqueous solution. For this purpose three experiment design approaches including fracional factorial design (FFD), path of the steepest ascent (PSA) and central composite design (CCD) were applied. With comparison to electrophoretic deposition and direct calcination, fabricated photoanode by anodization technique has shown the highest photocurrent because its construction is a 1-D structure. This kind of structure results in a shorter transmission path therefore can effectively prevent the electron-hole pair recombination. The application of design of experiment (DOE) has successfully optimized the efficiency of azo dye decolorization. In the FFD, the solution pH, cathode area, ratio of the electrolytes and initial concentration have been identified as key factors which have significantly affected the dye decolorization. These four factors were then controlled at the optimal conditions for optimize decolorization and degradation efficiency in the PSA study. The result of CCD study has shown the solution pH as the most significant factor that influence the decolorization efficiency. It has found that optimum dye decolorization occurs at pH 2.